They would have certainly been able to break the first three fetters and probably all ten fetters was an incorrect statement. I can understand that it is not possible in one lifetime and it would take many lifetimes. But for someone who dedicates more than half a century in austerity and studies the Buddha’s teachings, and is truly sincere, it is hard to believe that they would not have attained stream entry. There are probably many who may not achieve it in one lifetime, but there are also some exceptional monks and scholars. I have read somewhere,(probably on the puredhamma website) that only a Buddha is able to know and gauge a person’s spiritual progress. It is best to give these exceptional monks the benefit of the doubt.
Even in my life as a lay person I have experienced a guiding force that has helped me every step of the way. I have certainly stumbled and fallen flat from time to time, but have got up and got stronger in my attempts to redeem myself, and have seen a lot of good changes in my character.
I owe a debt of gratitude to all the monks and scholarly lay people’s talks I have listened to, and to the puredhamma website.
A Quest to Recover Buddha's True Teachings